Magnetic speedometer



April 12, 1938- v A. W. LE FEVRE ET A1. 2,114,191

MAGNETIC SPEEDOMETER Filed Jan. 1'7, 1936 27 2 I i f f 25/ l l l I. l

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Patented Apr. 12,

MAGNETIC srnanorm'rnn Arden W. Le Fevre and Thorolf Paul, Chicago, Ill., assignors to Stewart-Warner Corporation, Chicago, lll., a corporation of ,Virginia Application January 11, 193s, serial No. 59,567 comms. (crm-1s) This invention relates to magnetic speedometers and its object is to .provide a. structure of this character which shall be relatively light in weight, with extremely simple mechanism andv 5 with parts designed for economical manufacture and assembly. It consists of the features and elements of construction herein shown and described in combination, as indicated by the claims.

In the drawing: 1

Figure 1 is a face view of a speedometer embodying this invention.

Figure 2 is a rear view of the same.

Figure 3 is a diametral section taken as indicated at line/'3 3 on Figure 1, but on a larger scale.

Figure 4 is a detail section taken as indicated at line 4-4 on Figure 3, but on the same scale as Figure 2.

Figure 5 is a detail section taken as indicated at line 5 5 on Figure 3, but also on the same scale as Figure 2. a

'I'he speedometer embodying this invention is intended primarily as an inexpensive model adapted for use on bicycles. As shown in the drawing, the rotating element includes an annular magnet, I, having the usual gap at I between its vpoles and mounted on a pressed brass hub, 2, whose marginal portion is doubled back upon itself 3o at 2, and then extended in an annular ange, 2b, which nts snugly into the central opening in the magnet, I. 'I'he magnetv is thus seated against the shoulder formed by the doubled portion, 2, and is held frictionally on the flange, 2b, whose outer edge may be peened over at points, 2C, to effect a permanent securement. 'I'he web of the .hub member, 2, is similariy secured to the end of a shaft member, 3, formed with an enlargement,

3, which provides a shoulder against which thev 40 web of the pressed hub is held by peening over the extreme end of the shaft member at 3b. 'I'he shaft is formed with a bore, 3% extending inwardly from the other end. For a portion of the length of this bore, 3=, the shaft is constricted at 3d, to form a squared socket, 3, for interengagement with the terminal of a exible drive shaft in a well-understood manner. 'Ihe enlargement, 3, also provides a stop shoulder, tending to check endwise movement of the shaft in its bearing sleeve, 4, which is ixed centrally in the back of the casing, 5, and at the opposite end the shaft is reduced to` receive -a thrust washer, 6, and a collar, 1, the washer, 5,- engaging against a shoulder, 4*, in the counterbored outer end of the bearing, 4. Ilimited endwise playl of the shaft in its bearing is provided to ensure easy running. Preferably, for lightness, the casing, 5, is formed of thin sheet metal, such as aluminum or aluminum alloy, and to reinforce the back wall it may 'Y have radial ribs, 5l, formed at one side of the axis, the area at the other side being left plain so that a flat bracket arm, 8, may be secured thereto by` rivets, 9, to provide mounting means for the instrument. The ribs, 5', merge with a centrally offset portion, 5b, and the aperture at th`e center of this area is reinforced by washers, 5G, between winch the material of the casing is clamped when the washers are secured onto the reduced and shouldered end of the bearing member, 5, by peening over the extreme end portion, 4c, against the inner washer.

'I'he casing is also reinforced by the 'stiifening effect of a field cup, I0, of magnetic metal, having radial lugs, I Il, which are fastened permanently to the back wall of the casing, 5, by rivets, two of which may be the Vsame rivets, 9, which secure the bracket arm, 8. 'I'he field cup, I 0, ecloses the drag element, I2, which may be an aluminum disk with a peripheral iiange, I2, and which is accommodated in the space between the magnet, I, and the 'field cup, I0. The drag element, I2, is

carriednon a spindle, I3, having a pointed end journaled in a jewel bearing, I4, in the end `of the shaft, 3, and also journaled in a bushing, I5, carried at the center of the field cup, I0. The disk, I2, is provided with a hub, I6, which is forced onto a knurled` portion,-I3, of the shaft, I3. To check the drag element, I2, at its zero position this part, I2, has a lug, I2, bent forwardly to engage the lug, Iiid, bent back from the outer surface of the iield cup, I0.

A biasing spring, I l, is secured to a suitable g collar, I8, fast on the spindle, I3, and the outer end of the spring 1.11- anchored in a perforated lug, Inh, upstanding fromv the field cup, I0, to re. ceive a wedge pin, I 0. A hand or needle, I9, is secured to the end of the spindle, I3, by frictional engagement of its hub therewith.

'Ihe dial plate, 20, is formed with an annular ange', 20, and a short outwardly extending peripheral flange, 20", vdimensioned to iit respectively within the cylindrical wall of the casing, 5, and against its forward edge. A lug, 20c, engages a notch, 5, in the casing edge t definitely iix the dial against rotation. 'I'he cover glass, 2|, is fixed in the re-entrant bead, 22, of a bezel ring, 22, which has a rearwardly extended skirt, 22h, iit'- ting telescoplcally over the cylindrical casing, 5.

' A spacer ring, 23, is fitted between a should 22, ofthe bezel member and a ilange, 20h, of t e vtending therefrom and dial, thus limiting the extent to which the skirt portion, 22h, telescopes over the casing. i, and rmly retaining the dial plate, 20, in its proper plane. The edge of the glass, 2 i is lodged against a rubber gasket or sealing ring, 2l, disposed in the channel of the bezel ring, 22, and the glass is retained by a metallic ring, 25, of angular crosssection, forced into the bezel ring and overhanging the inner edge of the glass, 2|, with a paper gasket,'21, interposed asl seen in Figure 3. This mounting of the glass, 2l, in the bezel ring, 22, is independent of the other casing elements and can be completed before the ring, 22, is applied to the casing, 5. In the portion of the skirt, 22", which does not overlap the casing, d 22d, may be formed to admit lightr to the face of the dial plate,l2li, and a terminal cover, 26, of celluloid or the like may be secured over this opening to exclude made for illuminating the dial at night by rays from `a. special window in the vehicle headlight (not shown) or from a special small electric lamp bulb (not shown) near the window, 25, but shieldedso as not to glare into the eyes ofthe rider. f. y

As seenin Figures 3 andf, a temperature compensating shunt member, 30, is lodged between the pol l, of lthe magnet, i; this element is composed of ya, nickel steelalloy having an automatic compensating eiiect for temperature changes in an understood manner.

' While there is shown and described herein certainvspeciilc structure embodyingthe invention, it will be manifest to those skilled in the art that various modicatlons and re-arrangements of the parts may be made without departing from the spirit and the scope of the invention, and that the same is not limited to the particular form herein shown and described, except in so far as indicated by the appended claims'. We claim:

l. In. a magnetic speedometer, an annular magnet xed thereto, a bearing sleeve for the "shaft, a casing of light sheet metal having `a central aperture into which said sleeve is secured, and a field cup of magnetic metal concentrioally enclosing said magnet within the casing, said cup having outwardly extending portions at the edge of its cup form, and means securing said portions to the back wall of the casing to stillen it.

v2. In a magnetic speedometer, a rotary shaft, an annular magnet ixed thereto, a bearing sleeve for the shaft, a casing of light sheet metal having a central a. rture into which said sleeve is secured, said casing being formed with an annular boss around said aperture with radial ribs expressed into the back wall of the casing to stillen it.

3. In a magnetic speedometer, a cylindrical casing of light sheet metal, a dial plate stepped upon the edge of said casing and a bezel ring with. a deep annular flange telescopically engaging ,the

casing, said bezel having an offset forming a shoulder opposite said edge of the casing and a spacer interposed inturned bead, a cushion ring in said bead, a

dust. Thus, provision may be v' a rotary shaft,

protruding toward the web between said dial and the f shoulder, the outer edge of the bezel forming an.`

cover glass lodged'against the cushion and a retaining ring of angular cross-section encircling the edge of the glass and frictionally held in the cylindrical wall ofthe bezel between said bead and the plane of the shoulder to retain the glass independently of the dial and casing.

4. In a magnetic s Y meter, in combination a rotary shaftkan ann magnet fixed therete, a journal 'bearing for the shaft, a cup-form casing of sheet metal secured to said journal bearing at the center of its transaxial web and having its cup ange encompassing the magnet, a cup-formv drag element and aspindle .ilxedly secured at the center thereof and mounted with the spindle.,

5, a slot or window, Q. stepped in the end of the magnet shaft and with `the drag cup hoodin'g the magnet, a cup-form ileld member hooding the drag element and magnet and'made fast to the web of the cup-form casing by portions extending radially outward.

from its cup-form, annular disks embracing the web of the cup form casing at the fixed securement thereof to the journal bearing to reinforce the web, said web being formed with a plurality of radial embossments angularly distributed in an arcuate portion of its area between said reinforcing disks and the securement of the cup-form ileld member to the web, whereby the web of the casing is stiifened against'vibration due to jar of the instrument on a road vehicle.

5. In a magnetic speedometer, in combination a rotary shaft, an annular magnet ilxed thereto, a journal bearing for the shaft, a cup-form casing of sheet metal secured at the center of its transaxial web to the journal bearing, a cupform drag element and a spindle iixediy secured thereto at the center `oiE the cup form of the drag element, the spindle being stepped` in the end of the magnet shaft with the drag cup hooding the magnet, a cup form field member houding the drag element and magnet and made fast to the casing by means extending radially outward from its cup form to stiften said casing, the transaxal web of the drag element having an abutment of the held cup and the web of the field cup having an abutment protruding toward the web of the drag element, said abutments being positioned in said webs respectively for encounter with each other in the rotation of the drag element about its axis.

6. In a magnetic speedometer, a cylindrical casing with a dial plate, a cover glass, a bezel ring for the cover glass having an inturned portion bearing against the outer marginal portion of the glass with a cushion ring interposed and a retaining ring fitted into said bezel ring against the opposite side of the glass and frictionally held in the bezel, said bezel ring having a deep annu- 

